How to create a button to stop a clock

Hi there,

I have the following macro in my Module that shows the real time clock

Option Explicit

Public g_dtNextTick As Date


Sub UpdateTimer()

    With ThisWorkbook.Worksheets("Isotope Inventory")
      .Cells(1, 1).Value = Date
      .Cells(1, 2).Value = Time
    End With
    
    g_dtNextTick = Now + TimeSerial(0, 0, 1)

    Application.OnTime g_dtNextTick, "UpdateTimer"
End Sub

I also have the following macro in the workbook to keep the clock running whenever the workbook is opened.
However, this prevents me from editing the workbook such as unlocking cells
I'd like to create a button to stop the macro of the clock, allowing me to unlock any cells for editing
Any advice would be great! Thanks

Option Explicit

Dim mblnOpenMode    As Boolean


Private Sub Workbook_Activate()
    If mblnOpenMode Then
        mblnOpenMode = False
        Me.Worksheets("Isotope Inventory").Cells(1, 1).NumberFormat = "dd-mm-yyyy"
        Me.Worksheets("Isotope Inventory").Cells(1, 2).NumberFormat = "hh:mm:ss"
    End If

    Call UpdateTimer
End Sub


Private Sub Workbook_Deactivate()
    On Error Resume Next

    Application.OnTime g_dtNextTick, "UpdateTimer", Schedule:=False

    On Error GoTo 0
End Sub


Private Sub Workbook_Open()
    mblnOpenMode = True
End Sub

I also have the following